Virtually all types of human activities generate various types of waste or by-product materials. Many of these materials can be processed to yield substrates that are or may be readily converted into a useful product. Such conversion is desirable for at least three interrelated reasons. First, conversion reduces the load of material that ultimately must be disposed of via traditional waste management methods; second, conversion saves natural resources by more fully utilizing raw products; and third, conversion not only may save energy but may in fact contribute to the supply of energy yielding materials.
Waste has varied forms and characteristics. In terms of the regulation of waste disposal pursuant to federal statutes, rules and regulations, many waste materials are characterized as municipal solid waste pursuant to 42 USC 691 et seq. Other categories of waste materials include animal waste either as it exists in confined animal production facilities or as it may be found in confinement ponds or lagoons. Other wastes from specific industries that may, but are not necessarily included as municipal solid waste, include materials produced during food processing and rendering, wood and timber processing, and chemical and petroleum manufacturing and processing.
A need currently exists for an improved process and system for disposing of waste materials. In particular, a need exists for a process that can recycle and/or convert the materials into useful products.
In general, the present invention is directed to a process and system for producing useable products from organic materials, such as waste materials. For example, in one embodiment, the process of the present invention is directed to producing ethanol from organic waste materials. In this example, the process includes the steps of first collecting waste materials from various sources. The organic waste materials may include lignocellulosic materials, proteinaceous materials, carbohydrate materials, chitin waste materials, household garbage, restaurant waste, agricultural and forestry waste, petroleum or chemical manufacturing waste, or waste water. Any organic-bearing compound that can be oxidized may be used as a starting material. Waste materials can be pre-separated into organic and inorganic materials. If necessary, the waste materials can first be reduced into a smaller size by any of a variety of means such as shredding or grinding. Further, water can also be added to form a slurry that can be subsequently treated. In this slurry, organic materials exist in suspension and/or in true solution.
Once the slurry or solution containing the organic waste materials is prepared, the slurry is contacted with ozone. The ozone is present is an amount sufficient to convert at least a portion of the organic waste materials into a medium capable of being converted further by an organism, such as being converted into a fermentable medium. For most applications, the ozone should be fed to the aqueous solution at a concentration of at least 0.01 ppm. Desirably, for most applications, the ozone is fed at a concentration close to saturation. In order to increase the amount of ozone that is dissolved into the slurry/solution, the slurry/solution can be cooled if desired. In order to maximize oxidation after dissolution of ozone, the slurry/solution may be warmed to increase the rate of degradation of ozone to molecular oxygen and free radical oxygen.
During ozonation, the organic waste materials are oxidized and degraded into less recalcitrant materials. Complex carbohydrates such as cellulose are oxidized into a mixture of smaller molecules including sugars. Before, during or after ozonation, a base, such as a metal hydroxide, or an acid, can be added to the slurry to adjust the pH of the solution. By the ozonation process, the slurry is converted into a medium that is capable of sustaining biological metabolic processes.
After ozonation, the medium can be separated from any undissolved solids. Next, the medium is contacted with organisms which are capable of using the medium to produce a product. In one embodiment, microorganisms are contacted with the medium which causes the medium to undergo fermentation. For instance, microorganisms can be selected so as to produce ethanol from the fermentable substrate. The ethanol can then be collected and used as desired. Ethanol is known to be an effective energy source.
In order to collect the ethanol, the ethanol can be separated from the remainder of the aqueous solution. For instance, the solution produced after fermentation can undergo a distillation process for isolating the ethanol. One skilled in the art will recognize that there are many other ways of collecting products including centrifugation, temperature fractionalization, chromatographic methods and electrophoretic methods. Some products may be gaseous and can be collected by typical gas collection methods.
In another embodiment of the present invention, instead of being converted into ethanol, the oxidized waste materials can be converted into a hydrocarbon gas, such as methane. For example, a genus of methane-producing bacteria is Methanobacterium. In this embodiment, the converted medium can be fed directly to the methane-producing organism or, alternatively, the medium can first be converted into ethanol and then fed to the methane-producing organism. Once produced, the methane can be collected in various ways and used as desired.
It should be understood, however, that the process of the present invention can be used to produce other useful products through bioconversion in addition to alcohols and hydrocarbon gases. For example, the products produced by bioconversion of the substrate can be altered by varying the organisms used in the system. The organisms contacted with the slurry can be carefully collected in order to optimize process conditions. The organisms can be, for instance, bacteria, yeast, fungi, algae, genetically engineered microorganisms, or tissue culture. Both prokaryotic and eukaryotic organisms or mixtures thereof can be cultured in the ozonated substrate. The product may be intracellular or extracellular in nature. The product may be particulate, liquid or gaseous. The product may be miscible or immiscible in water. Other products that can be formed according to the present invention include other alcohols, aldehydes, ketones, organic acids, purines, pyrymidines, alkanes, alkenes, alkynes, ethers, esters, amines, proteins, amides, cyclic and aromatic compounds, enzymes, pigments, lipids, phospholipids, peroxides, gums, pharmaceuticals such as vitamins, microbial cellulose and other polymers.
Any of the oxidized and converted organic materials that are not used in the process can be fed to a plant system, such as an algae system, and used for irrigation and/or as a food source. The plant system can also remove inorganic and/or heavy metal substances. If necessary, prior to being fed to the plant system, the aqueous solution containing the converted organic materials can be reozonated.
Other features and advantages of the present invention will be apparent from the following description.